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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 163 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.13 + 9 =
  2. 2.73 + 19 =
  3. 3.28 − 19 =
  4. 4.69 − 9 =
  5. 5.721 + 99 =
  6. 6.73 − 29 =
  7. 7.39 − 19 =
  8. 8.362 − 99 =
  9. 9.15 + 9 =
  10. 10.71 + 19 =
  11. 11.40 + 19 =
  12. 12.89 − 29 =
  13. 13.503 − 99 =
  14. 14.396 + 99 =
  15. 15.206 + 99 =
  16. 16.78 + 9 =
  17. 17.59 + 9 =
  18. 18.32 + 19 =
  19. 19.678 − 99 =
  20. 20.23 + 29 =
  21. 21.622 + 99 =
  22. 22.49 − 29 =
  23. 23.37 − 19 =
  24. 24.621 + 99 =
  25. 25.25 + 19 =
  26. 26.75 − 9 =
  27. 27.87 − 29 =
  28. 28.30 − 19 =
  29. 29.668 + 99 =
  30. 30.28 + 19 =
  31. 31.38 − 9 =
  32. 32.59 − 9 =
  33. 33.294 − 99 =
  34. 34.664 − 99 =
  35. 35.19 − 9 =
  36. 36.56 + 29 =
  37. 37.90 − 29 =
  38. 38.122 + 99 =
  39. 39.36 + 19 =
  40. 40.62 − 29 =

Answer key

  1. 22
  2. 92
  3. 9
  4. 60
  5. 820
  6. 44
  7. 20
  8. 263
  9. 24
  10. 90
  11. 59
  12. 60
  13. 404
  14. 495
  15. 305
  16. 87
  17. 68
  18. 51
  19. 579
  20. 52
  21. 721
  22. 20
  23. 18
  24. 720
  25. 44
  26. 66
  27. 58
  28. 11
  29. 767
  30. 47
  31. 29
  32. 50
  33. 195
  34. 565
  35. 10
  36. 85
  37. 61
  38. 221
  39. 55
  40. 33

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